--that you don't have exclusively a small-fiber syndrome; all small, unmyelinated fibers are sensory/autonomic and don't enervate muscle (all motor fibers are meylinated).

Unfortunately, many neuropathies, particularly toxic ones, can affect disparate types of fibers. There are even cases in which syndromes that appear exclusively small fiber at first slowly spred to the larger ones. These are those in which the damage is initially axonal--the nerve fiber is itself attacked, rather than the myelin sheathing, although there can be secondary damage to that. And many toxic neuropathies are primarily axonal:

http://neuromuscular.wustl.edu/nother/toxic.htm

Of course, loss of muscle can also occur from disuse, and toxic exposure can result in myopathy as well as neuropathy (this has happened notably with the statins).